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The Reproductive Cycle of Whiptail Lizards

By Anne Woods

Whiptail lizards live throughout the western United States, with numerous species concentrated in the Sonoran Desert and some, such as the western whiptail, ranging as far north as Idaho and Oregon. These lizards prefer dry climates and seek out habitats with sparse vegetation, such as desert grass, pine, sagebrush, scrub and oak. Depending on the species, they reproduce asexually, sexually or even both.

Overview

Most whiptail lizards' bodies measure from 3 to 5 inches, not counting the tail. Depending on the species, they can be brown, tan, red, black, olive or gray, and their backs usually feature lighter spots or stripes. Their diet includes insects such as beetles, crickets, grasshoppers and termites, although they also sometimes eat spiders and scorpions. Whiptail lizards are most active on summer mornings and late afternoons, and their reproductive cycle usually takes place between April and August.

Parthenogenesis

Several species, such as the Sonoran spotted and desert grassland whiptails, consist of females only. They reproduce through an asexual process called parthenogenesis, which begins with a simulated mating ritual in which the females bite and mount each other. Scientists believe this behavior causes them to produce and lay unfertilized eggs. The young that hatch are genetic clones of their mothers. Females of a few parthenogenetic species, such as checkered and New Mexico whiptails, occasionally breed with males of other whiptail species.

Sexual Reproduction

Most whiptails are not parthenogenetic; instead, reproduction occurs after males and females mate. As in the female-only courting ritual, the males mount and bite their partners. They use their hemipenes—a pair of reproductive organs at the tail’s base—to fertilize the eggs. After mating, females can hold on to the sperm for future use.

Eggs

Whether they reproduce sexually or asexually, female whiptail lizards bury their egg clutches. In the warm desert regions of southern California, Arizona and New Mexico, they can lay two or three clutches during a summer. In the northern parts of their range, such as Colorado and Idaho, they lay only one. Clutches average about three eggs, although depending on the species, the female could lay four, five, six or more at a time. Juveniles usually hatch during July or August, after two to two and a half months of incubation. The lizards become sexually mature when they’re 1 or 2 years old.